Temperature control



Jfine 28, 1955 MARTIN 2,712,073

TEMPERATURE CONTROL Filed Oct. 51, 1944 32 INVENTOR.

4'0 'nzmeif amariz'n BY Ma M 14 1r 16 Kai-E M r X United States PatentTEMPERATURE coNTRoL Emmett V. Martin, Oak Ridge, Tenn., assignor, bymesne assignments, to the United States of America as represented by theUnited States Atomic Energy Com- IIllSSlOll Application October 31,1944, Serial No. 561,271

12 Claims. (Cl. 250-419) The invention described herein relates to thefield of isotope separation, that is separation of ions having differentmass-energy properties. It is particularly concerned with equipmentwherein the ion source includes means for volatilizing a material to beionized by the controlled application of heat to the material.

Heretofore in equipment of this nature it has been the practice tovolatilize the material to be ionized, and to maintain the material in avapor state by the applicaitself, which, as mentioned, includes arelatively high intensity electron stream for bombarding the vapor ofthe volatilized charge, constitutes a relatively unsteady source ofconsiderable heat, and since this heat may be quite readily conducted tothe charge itself, it becomes difiicult to accurately maintain thetemperature of the charge. An object of my invention is to meet thedifficulty by employing an automatic control system having athermostatic means so located, with reference. to the structure, thatthe thermostatic means is affected by heat from the ionizing means tothe same extent that the charge being volatilized is atfected thereby.Thus the thermostatic means is able to dampen out variations of thetemperature of the charge which would otherwise result from heatconducted thereto from the ionizing means.

Another object of my invention is to supply heat to the vaporized chargein the vicinity of the ionizing means to maintain it in a vaporizedstate and to control this heat in response to the thermostatic meanswhich controls the main heat for volatilizing the charge. preferred formof the invention, the heating means which provide heat for volatilizingthe charge and for maintaining the charge in a vapor state in thevicinity of the ionizing means are electrical heating elements connectedin parallel.

Other objects and advantages of my invention will become apparent fromthe following detailed specification and annexed drawings, wherein:

Fig. 1 is a diagrammatic view of an isotope separator including an iongenerator in which the control arrangement of my invention may bepracticed.

Fig. 2 is a view of the control arrangement of my invention applied toan ion producing source of the type which may appropriately be used inthe system of Fig. 1.

Referring to Fig. 1 of the drawings, there is shown diagrammatically anapparatus for isotope separation, the apparatus including ion generatingmeans wherein a solid material is volatilized by the application ofheat, my invention being particularly adapted to the control of theapplication of heat for volatilizing the material and thereaftermaintaining it in a vapor state during ionization. The'apparatus of Fig.l is of the type disclosed in greater In the 2,712,673 Patented June 28,1955 'ice detail in the application of Ernest 0. Lawrence, Serial No.557,784, filed October 9, 1944. The apparatus of Fig. 1 includes a tank10 the interior of which is evacuated to a relatively high degree ofvacuum as will be presently explained. The tank 10 is rectangular incross section, and one side of the tank is closed by a relatively heavyface plate 11 which is attachable to the tank by means of screw clamps12 and 13, there being provided suitable bearing surfaces on the faceplate 11 and on the tank 10 so that when the face plate 11 is clamped inposition, it engaged the tank in sealing relationship so as to insureagainst loss of vacuum at the joint. All of the mechanism within thetank 10 is attached to and carried by the face plate 11 as will bepresently explained.

The tank 10 has a number of windows 14, 15, 16, and 17, so as to make itpossible to watch operations within the tank, and it has a largedischarge outlet through which the air and moisture within the tank areevacuated. The discharge outlet 20 is connected to dilfusion pumps,indicated diagrammatically at 21, by a suitable connection, asshown, andthe difiusion pumps 21 are backed by, that is connected to, a mechanicalpump or pumps 22, these pumps being of the rotary type. They may beKinney pumps for example.

Within the tank 10 is a liner structure 23 which forms an arcuateconduit for a beam or beams of ions generated at the left end of theliner and terminating adjacent the right end thereof. The liner 23 andits associated apparatus is carried from the face plate 11 by thesupporting structure, designated generally by the numerals 24 and 25,and by the brace indicated by numeral 26.

Adjacent the left end of the liner 23 are disposed a pair ofvolatilizing chambers and 31 in which a charge of solid material to beionized is volatilized. My invention is primarily concerned with thecontrol of the application of heating to the chambers 30 and 31, thechamber 30 with its associated heating elements and automatic controltherefor being shown in greater detail in Fig. 2. Since the two chambersand their associated equipment are identical, only one will be describedin detail.

Referring now more particularly to Fig. 2, the chamber 30 may preferablybe generally cylindrical. It includes a lower portion 32 and a smallerupper portion or chamber 33 connected to the lower portion by adiverging passageway or throat 34. Numeral 35 designates a charge bottleadapted to contain a charge of the solid material to be volatilized andshaped so as to fit within the lower part 32 of chamber 30. The chargebottle 35 has an opening 36 in its top through which the volatilizedmaterial may pass upwardly. The upper chamber portion 33 has a bottom 37with spaced openings 38 and 39 therein to allow the vapor to pass upinto the portion 33. Extending across the interior of the chamberportion 33 is a plate or baffle 40 having openings 41 and 42 near itsedges to permit the upward travel of the volatilized charge. The chamberportion 33 also has an opening 43 in its top in the form of a relativelylong and narrow slit, and the vapor from the volatilized charge passesupwardly through this slit. Near one end of the slit 43, and adjacent aslit 45, is a filament 44 to which a suitable voltage is applied forheating it, as will presently be described, and from which electrons areemitted near the end of the slit 43. The filament and its operation willbe referred to presently.

The lower portion 32 of chamber 30 is heated by an electric heatingelement and the upper portion is heated by another electric heatingelement 51. The operation of the electric heaters and the automaticcontrols therefor will be described presently.

Referring again to Fig. 1, above the chamber 30 and adjacent thereto isa member 52. which may preferably be I made of carbon, and which hastherein a slit 53 which is directly above and parallel to the slit 43 ofchamber portion 33. The member 52 is electrically connected to a similarmember above the chamber 31, the apparatus associated with the twochambers being identical as previous ly pointed out. The member 52constitutes an electrode which is maintained at a certain potential, aswill presently be described, for accelerating a beam of ionizedparticles passing upwardly through the slit therein. Above the member 52is a conical throat-shaped member 54 through which the beam passingupwardly through the slits 53 and 43 passes into the liner 23.

The entire tank is disposed within a relatively intense magnetic fieldproduced. by windings indicated diagrammatically at 57 which completelyencircle the tank and liner as indicated, the direction of the fieldbeing perpendicular to. the. plane of. the drawing. The direction of thefield is therefore parallel to the slits 43 and 53.

The face plate 11 is grounded as shown and the liner 23 and the members52 are maintained at relatively high negative potentials by conductorswhich are fed into the interior of the tank It through a conduit 58which extends through a sealing device 59 in face plate 11. The liner 23is maintained at a relatively high negative potential V1 by means of aconductor 60, and the member 52 is maintained at a relatively highnegative potential V1+V2, which is higher than the potential of liner23, by means of a conductor 61. The operation of the ion generatingapparatus as so far described is that the vapor of the volatilizingcharge in the bottle passes upwardly into the chamber portion 33 whereit is maintained in vapor state by the electric heating element 51, thevapor then passing upwardly through the slit 43. Energization of thefilament 44 causes electrons to be emitted therefrom, which electronsare collimated to form a beam in the slit 43 by the action of themagnetic field, which, as has been previously described, is in adirection to the slit. The electrons bombard the particles of the vaporpassing upwardly through the slit 43 so as to form ions which areaccelerated upwardly in the form of a beam through the slit 53 in theelectrode 52, which, as described above, is maintained at a relativelyhigh negative accelerating potential. The beam of ions passes upwardlythrough the throat 54 and the effect of the magnetic field upon the beamis to bend it into an arc of a circle within the liner 1.3, the beamtraveling around through the liner so as to be received in a receivingchamber adjacent the right end of the liner 23. The receiving chamber 65is in the form of a box having a shape which in cross section is asshown in Fig. l. The receiver 65 may be adjusted laterally by stem 66operating through linkages 67 and it may be adjusted vertically by astem 68, the stems passing through suitable sealing devices 69 and 7 0,respectively, associated with the face plate 11. The receiver 65 haspockets 71 and 72 therein which are so located as to receive certaincomponents of the beam which travels around through the liner 23, itbeing understood that various components of the beam travel in arcs ofcircles of different radii depending upon the mass-energy properties ofthe different components. Within the pockets 71 and 72 are electrodes 73and 74, respectively, which are maintained at the negative potential V1by means of conductors 75 and 76 which are led out of the tank 10through a conduit 77 similar to the conduit 58, the conduit 77 passingthrough the face plate 11 byway of a sealing device 78 associated withthe face plate. The electrodes 73 and 74 are at the point of focus ofthe components of the beam which it is desired to collect, the desiredisotopes collecting in the pockets 71 and 72 during operation.

Numeral 81 designates a manually operated shutter which may be moved toa position in front of the window 17 by means of an operating stem 82extending through a sealing device 83.

It will be understood, of course, that those elements Cir which aremaintained at high potential are suitably insulated from other elementsat lower or ground potential. Also as described in the applicationpreviously referred to, various of the parts within the tank It may becooled by a suitable water cooling system, and shielding may be providedat appropriate points to protect the mechanism from becoming coated as aresult of being contacted by the vapor from the charge bottle and forprotection from deterioration which may necessarily result from theprocess.

In carrying out the ionizing and isotope separating process, it isnecessary that the charge bottle 35 be maintained accurately at atemperature within 2 of the desired volatilizing temperature. Thechamber portion 33 must be maintained at a relatively highertemperature, sufficiently high so as to maintain the material within thechamber portion 33 in a vapor state so that it can be appropriatelyionized by bombardment of the electron stream. The electric heatingelements 50 and 51 are connected in parallel, as shown, and to thesecondmy 85 of a transformer 86 having a primary winding 87. Theelectric heating elements 50 and 51 may be of the well known Calrod typeand are of sufficient heating, capacity so as to produce the requiredheating in. the

.; chamber portions 32 and 33. Both of the electric heating elements arecontrolled by a control system which includes, as the primary controlelement, thermocouple 88. situated in the throat 34 so that it isaffected by heat produced by both of the electric heating elements 50and 51. That is, the thermocouple 88, which is suitably shielded,responds to a temperature at a point in the temperature gradient acrossthroat 34, it being remembered that the chamber portion 33 is maintainedat a higher temperature than the chamber portion 32, the relativecapacities of the heating elements being such as to cause a highertemperature to be maintained in the chamber portion 33. The beam ofelectrons or are, which has been described with reference to slit 43,and the accelerating electrode 52 generate a considerable amount ofheat, and this source of heat during operation is relatively unsteady.This heat can be transferred to the charge in the charge bottle quitereadily by conduction. It is an object of my arrangement therefore toprevent this heat from changing the temperature of the charge inthecharge bottle without the thermostatic element 88 being similarlyaffected. The position of the thermocouple 88 is therefore such that theheat from the ionizing means affects the thermocouple and the charge inthe charge bottle substantially similarly. The thermocouple 88 is,therefore, able to control the temperature at the charge bottle withaccuracy even though the heat generated by the ionizing means isunsteady.

The control system which I prefer to use includes a potentiometer device89 which is automatically adjusted in accordance with the amount thatthe temperature affecting thermocouple 88 deviates from a set value. Thedevice 89 may preferably be the instrument known as the Micromaxmanufactured by the Leeds & Northrup Company. The device 89 impresses avoltage signal upon an electronic control device 90 which mayappropriately be the Reactrol control device manufactured by the GeneralElectric Company. The device 90 controls the amount of current flowingin the D. C. winding 91 of a saturable reactor 92 having A. C. windings93 and 94. Saturable reactor 92' is connected to the primary winding 87of transformer 86 and controls the amount of power supplied thereto froma source of power designated by the numeral 95. Controls 89, 90, and thesaturable reactor 92 constitute a system of control which is well knowin the art and which in itself forms no part of the invention.

In operation of the controls of Fig. 2, upon a rise in temperatureaffecting the thermocouple 88, a voltage signal is impressed on thecontrol device 90 which causes the amount of current flowing in the D.C. saturatingwinding 9 1 to be decreased. This decreases the saturationof the saturable reactor 92 thereby increasing its impedance anddecreasing the power supplied to the transformer 86'. The amount of heatsupplied by the heating elements is thus reduced and the temperaturereduced to the desired value. ture at the thermocouple 88 the operationis in the oposite direction and the amount of heat supplied is increasedto bring the temperature back to the desired value.

By positioning the thermocouple 88 in the manner described where it isaffected by heat from the ionizing means to the same extent that thecharge in the charge bottle is, it is possible to maintain thetemperature of the charge bottle with accuracy at the desired value. Thethermocouple at the same time exercises control over both of theelectrical heating elements which -are-connected in parallel, and thetemperature in the vicinity of the ionizing means is thereby maintained.high enough to maintain the charge in that vicinity in a vaporizedstate. My invention provides an effective and eflicient way ofmaintaining the temperature ,of the charge being volatilized accuratelyat the desired value, and the position of the thermocouple 88 andassociated control mechanism is such that removal and insertion of thecharge bottle is not prevented or interfered with.

The embodiment of my invention which I have disclosed is representativeof a preferred form and adaptation thereof. The invention is to belimited not by the disclosure but only in accordance with the scope ofthe claims appended hereto.

I claim:

1. In apparatus of the character described, in combination, containingmeans for a material to be vaporized,

heating means associated with said containing means for vaporizing'saidmaterial, said heating means including means situated adjacent aposition normally occupied by vapor of said material, temperatureresponsive means controlling the heating means, said temperatureresponsive means being situated at an intermediate point as respectssaid containing means and said position so as to be affected by both thetemperature in the region wherein vaporization is taking place and alsothe region normally occupied by vapor.

2. In apparatus of the character described, in combination, containingmeans for a material to be volatilized, heating means associated withsaid containing means for volatilizing said material, said heating meansincluding means situated adjacent a position normally occupied by vaporof said material, means for ionizing said material in the vicinity ofsaid position, temperature responsive means controlling the heatingmeans, said temperature responsive means being situated at an intermediate point as respects said containing means and said position so asto respond to both the temperature in the region wherein vaporization istaking place and the temperature in the vicinity of the ionizing means.

3. In apparatus of the character described, in combination, containingmeans for material to be vaporized, heating means associated with saidcontaining means for vaporizing said material, means disposed at aposition normally occupied by vapor for ionizing the vapor of saidmaterial, said ionizing means including electrical apparatus whichgenerates an unsteady flow of heat during operation, temperatureresponsive means controlling the heating means, said temperatureresponsive means including an element situated at an intermediate pointas respects said material and said position so that heat from saidionizing means substantially similarly affects said temperatureresponsive means and said material being volatilized so that thetemperature responsive means may accurately control the temperature ofthe material being volatilized even though the how of heat from saidionizing means is unsteady.

4. An. apparatus of the character described, in com- Upon a fall intemperabination, containing means for material to. be volatilized,heating means associated with said containing means for volatili zingsaid material, means for ionizing vapor of said material, said ionizingmeans including electrical apparatus which generates an unsteady flow ofheat during operation, said heating means including means formaintaining said material .in a vapor state in the vicinity of saidionizing means, temperature responsive means controlling said heatingmeans, said temperature responsive means including an element situatedat an intermediate point as respects the material being volatilized andthe ionizing means so that heat from the ionizing means substantiallysimilarly affects said element and said material being volatilized sothat the temperature responsive means is able to accurately control thetemperature of the material being volatilized even though the flow ofheat from the ionizing means is unsteady.

5. In apparatus of the character described, in com-j bination,containing means for material to be vaporized, heating means forvaporizing said material associated with said containing means, saidcontaining means including a vapor containing chamber and a passagewayforming means for conveying vapor to said chamber, said heating meansincluding means associated with said chamber having sufficient heatingcapacity to maintain a relatively higher temperature in said chamber soas to prevent condensation therein, and temperature responsive means forcontrolling said heating means, said temperature responsive meansincluding an element responsive to the temperature at a point in thegradient between the material being vaporized and said chamber.

6. In apparatus of the character described, in combination, containingmeans for material to be vaporized, heating means for vaporizing saidmaterial associated with said containing means, said containing meansincluding a vapor containing chamber and a passageway forming means forconveying vapor to said chamber, said heating means including meansassociated with said chamber having sufficient heating capacity toprevent condensation therein, means for ionizing material which has beenmaintained in a vaporized state in said chamber, and temperatureresponsive means for controlling said heating means, said temperatureresponsive means including an element responsive to temperature at apoint in the region of said passageway forming means affected by heatfrom said heating means and said ionizing means.

7. In apparatus of the character described, in combination, containingmeans for material to be volatilized, heating means for volatilizingsaid material associated with said containing means, said containingmeans including a vapor containing chamber and a passageway formingmeans for conveying vapor to said chamber, means for ionizing vaporizedmaterial in said chamber, said ionizing means including an electricalapparatus which generates an unsteady flow of heat during operation,temperature responsive means for controlling the temperature of theheating means for volatilizing the material, said temperature responsivemeans including an element responsive to temperature at a point in thetemperature gradient existing between said material being volatilizedand said chamber, the position of said temperature responsive elementbeing such that heat from said ionizing means substantially similarlyaffects said element and said material being volatilized so that thetemperature responsive means is able to accurately control thetemperature of the material being volatilized even though the flow ofheat from said ionizing means is unsteady.

8. In apparatus of the character described, in combination, containingmeans for material to be vaporized, heating means associated with saidcontaining means for vaporizing said material, said heating meansincluding means situated in a position wherein it is desired to preventcondensation of vapor, means for ionizing said material in the vicinityof said position, means forming a vacuum chamber enclosing at least apart of said heating means and said ionizing means, means for evacuatingthe air from said chamber, temperature responsive means controlling theheating means, said temperature responsive means including an elementsituated at an intermediate point as respects said material and saidionizing means so as to be affected by both the temperature in theregion wherein vaporization is taking place and the temperature in thevicinity of the ionizing means.

9. In apparatus of the character described, in combination, containingmeans for material to be volatilized, heating means for volatilizingsaid material associated with said containing means, said containingmeans including a vapor. containing chamber, ionizing means for ionizingvapor of said material, said ionizing means including electricalapparatus which generates an unsteady llow of heat during operation.said heating means comprising parallel connected electrically heatingelements, one of said elements being arranged to generate heat forvolatilizing said material and the other of said elements being arrangedto supply heat for maintaining said material in a vapor state in thevicinity of said ionizing means, temperature responsve means forcontrolling said heating means, said temperature responsive meansincluding an element situated at an intermediate point as respects saidmaterial and said ionizing means such that heat from said ionizing meanssubstantially similarly afiects said element and said material beingvolatilized so that the temperature responsive means is able toaccurately control the temperature of the material being volatilizedeven though the flow of heat from said ionizing means is unsteady.

10. In apparatus of the character described, in combination, containingmeans for material to be vaporized, heating means for vaporizing saidmaterial associated with said containing means, said containing meansincluding a vapor containing chamber and a passageway forming means forconveying vapor to said chamber, said heating means including meansassociated with said chamber having sufiicient heating capacity toprevent condensation therein, means for ionizing material which has beenmaintained in a vaporized state in said chamber, means forming a vacuumtank inclosing said chamber, its associated heating means and saidionizing means, means for evacuating the air from said tank, andtemperature responsive means for controlling said heating means, saidtemperature responsive means including an element responsive to thetemperature of said passageway forming means.

11. In apparatus of the character described, in combination, containingmeans for material to be vaporized, said containing means having anoutlet for vapor in its upper part, heating means associated with saidcontaining means for vaporizing said material, means for ionizing saidvapor adjacent said outlet and spaced from the said material to bevaporized, additional heating means adjacent to the ionizing means forpreventing condensation of vapor in that vicinity, temperatureresponsive means controlling all of the heating means, and including atemperature responsive element located at a point intermediate the firstheating means and the ionizing region so as to be responsive to heatfrom all of the heating means and from the ionizing means and to beexposed to heat from the ionizing means to sub- 3 stantially the sameextent as the material to be vaporized is exposed thereto.

12. The structure of claim 11, wherein a converging passageway isprovided to communicate vaporized ma terial to the ionizing means andthe temperature responsive element is located at a point in saidconverging passageway.

References Cited in the file of this patent UNITED STATES PATENTS2,149,729 Finch Mar. 7, 1939 2,189,618 Slepian Feb. 6, 1940 2,192,047Miles Feb. 27, 1940 2,221,467 Bleakney Nov. 12, 1940

11. IN APPARATUS OF THE CHARACTER DESCRIBED IN COMBINATION, CONTAININGMEANS FOR MATERIAL TO BE VAPORIZED, SAID CONTAINING MEANS HAVING ANOUTLET FOR VAPOR IN ITS UPPER PART, HEATING MEANS ASSOCIATED WITH SAIDCONTAINING MEANS FOR VAPORIZING SAID MATERIAL, MEANS FOR IONIZING SAIDVAPOR ADJACENT SAID OUTLET AND SPACED FROM THE SAID MATERIAL TO BEVAPORIZED, ADDITIONAL HEATING MEANS ADJACENT TO THE IONIZING MEANS FORPREVENTING CONDENSATION OF VAPOR IN THAT VICINITY, TEMPERATURERESPONSIVE MEANS CONTROLLING ALL OF THE HEATING MEANS, AND INCLUDING ATEMPERATURE RESPONSIVE ELEMENT LOCATED AT A POINT INTERMEDIATE THE FIRSTHEATING MEANS AND THE IONIZING REGION SO AS TO BE RESPONSIVE TO HEATFROM ALL OF THE HEATING MEANS AND FROM THE IONIZING MEANS AND TO BEEXPOSED TO HEAT FROM THE IONIZING MEANS TO SUBSTANTIALLY THE SAME EXTENTAS THE MATERIAL TO BE VAPORIZED IS EXPOSED THERTO.